Builder mircemk used a 2.1-inch CrowPanel Rotary Display, combining an ESP32-S3 with a 480x480 round touchscreen and a rotary encoder, to create a countdown timer with code that is fully open and flashable.
The build adds a PCF8574 I2C I/O expander to drive a buzzer for end-of-countdown audio feedback. The rotary encoder ring sets the time with a twist, the display graphics rotate in sync, and the screen shifts color as the countdown approaches zero, readable from across a room.
What makes this worth reading in full is the design reasoning: how a commodity smartwatch-era circular display, falling in cost, maps almost perfectly onto a classic kitchen timer interaction model, and where else builders are taking these panels, including desktop flight radar displays.
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